Introduction to Computer Systems - Fundamentals of Computer Organization and Architecture - page 13

8. A compiler designer is trying to decide between two code sequences for a
particular machine. The hardware designers have supplied the following
facts:

Instruction
class

CPI of the
instruction class

A 1

B 3

C 4

For a particular high-level language, the compiler writer is considering two
sequences that require the following instruction counts:

Instruction counts
(in millions)

Code
sequence

AB C

1 2 1 2

2 4 3 1

What is the CPI for each sequence? Which code sequence is faster? By how
much?
9. Consider a machine with three instruction classes and CPI measurements as
follows:

Instruction
class

CPI of the
instruction class

A 2

B 5

C 7

Suppose that we measured the code for a given program in two different
compilers and obtained the following data:

Instruction counts
(in millions)

Code
sequence AB C

Compiler 1 15 5 3

Compiler 2 25 2 2